Originally Posted by Andriyko

There is only one PNR where you can (and should) manage a specific flight. If you booked prime BA flights and AA*BA codeshares in a single reservation then BA will create two PNRs - one for the prime flights and one for its flights booked as AA codeshares (operational PNR). When you go to MMB look whether the flight is listed as 'confirmed' or 'information only'. Manage a specific flight in the PNR where it is listed as 'confirmed'.